Adsorbents and methods for the separation of ethylene and propylene and/or unsaturated hydrocarbons from mixed gases

ABSTRACT

Adsorbents useful in the selective adsorption of unsaturated hydrocarbons, the manufacture of the adsorbents, and processes for the separation of unsaturated hydrocarbons using the adsorbents.

BACKGROUND OF THE INVENTION

[0001] 1. Technical Field of the Invention

[0002] This invention relates to a new adsorbent useful in selectiveadsorption of unsaturated hydrocarbons, the manufacture of the adsorbentand a separating process employing the same. More specifically, thisinvention relates to an adsorbent having a high degree of selectivityand affinity for olefin molecules and also having high adsorptioncapacity for olefins, and a process for producing the same. Morespecifically, this invention relates to an ethylene and/or propyleneseparation process employing a specially prepared adsorbent toeffectively separate ethylene and/or propylene from a mixed gascontaining ethylene and/or propylene together with a component selectedfrom the group consisting of H₂, He, CH₄, C₂H₆, C₃H₈ and mixturesthereof, in an efficient manner using a developed adsorbent having ahigh adsorptive capacity for unsaturated hydrocarbons such as ethyleneand propylene.

[0003] 2. Description of Related Art

[0004] Unsaturated hydrocarbons such as ethylene and propylene are basicraw materials in synthetic chemistry. These are produced bynaphtha/natural gas cracking or by dehydrogenation of paraffin.Invariably these are obtained as mixtures necessitating separationbefore their use. Traditionally separations of ethylene from ethane andpropylene from propane have been achieved by low temperature and/or highpressure distillation. These separations are highly energy intensive anddifficult to achieve. Separation of mixture of ethane-ethylene iscarried out by at −25° C. and 320 psig in a distillation columncontaining over 160 trays and propane-propylene at −30° C. and 30 psigpressure in a distillation column containing over 200 trays [1]. It issaid that separations of ethane-ethylene and propane-propylene bydistillation are the largest energy consuming separation processes inpetrochemical industry. Further, demand for ethylene and propylene isever increasing.

[0005] For the past several years, various researchers have been workingon the development of alternative technologies such as adsorption,chemical absorption and membrane separation processes. Of the variousalternate technologies, adsorption process appears to be promising [2].Conventional adsorbents such as activated alumina, activated carbon,silica gel and zeolites do not show good selectivity for olefins overparaffins. Hence, development of a suitable adsorbent has become a keyfactor for the successful development of adsorption process.

[0006] Some of the adsorbents that have been reported forparaffin-olefin separation are crystalline CuCl [3-5]; ion exchangedzeolites [6-7]; polymer supported aluminum silver chloride [9-11]; andcopper-containing resins [12]. Most of these adsorbents suffer from oneor the other drawbacks such as slow adsorption kinetics, poor adsorptioncapacity, and/or selectivity. More recently Yang and Kikkinides [8], andCho and coworkers [13] have reported more promising adsorbents. Amongthe adsorbents reported by them, Ag⁺ resin and CuCl/Al₂O₃ showed higholefin adsorption capacity and good selectivity. However, ethylene andpropylene sorption kinetics on Ag⁺ resin are slow. CuCl/Al₂O₃ is a CuCldispersed on γ-Al₂O₃ by monolayer dispersion technique and hence, isobtained in powder form. For commercial use this adsorbent needs to beformed in to pellets which leads to reduction in adsorption capacity andselectivity. Further, adsorbent formulations prepared using Cu(I)compounds are unstable and easily get oxidized to Cu(I) leading to lossin adsorption capacity and selectivity of the adsorbent. Xie et al.[14-15], have also reported a series of adsorbents containing Cu(I).These were also prepared in powder form. Hence, these adsorbents alsosuffer from the above mentioned drawbacks.

SUMMARY OF THE INVENTION

[0007] It has now been found that a group of solid adsorbents in theform of pellets/beads have high adsorptive capacity and selectivity forethylene and/or propylene not known in the prior art and that they canbe produced by a simple process as described below. These adsorbentscomprise (i) a silver compound and (ii) a support having a sufficientlyhigh surface area on which support said silver compound is supported.These adsorbents are highly stable and are capable of reversiblyadsorbing substantial quantity of ethylene and/or propylene at roomtemperature. The rates of adsorption of ethylene and/or propylene arealso very fast in these adsorbents.

[0008] It is an object of the present invention to provide a process forproducing new highly stable solid adsorbent in pellet/bead form forselective adsorption of unsaturated hydrocarbons, which adsorbent is acomposite comprising (a) a silver. compound and (b) a suitable supporthaving a sufficiently high surface area, at least a portion of saidsilver compound being supported by said support, and which adsorbent isobtainable by a process comprising impregnation of silver compound in asaid support and heat treatment of thus obtained adsorbent. Optionallythe adsorbent may also contain a promoter compound.

[0009] It is another object of this invention to provide a process forthe separation of ethylene and/or propylene from a mixed gas containingethylene and/or propylene together with another component selected fromsuch as H₂, He, CH₄, C₂H₆, C₃H₈ and mixtures thereof, which processcomprises passing a stream of said mixed gas through a mass of theadsorbent at a temperature from 0° C. to 100° C. and a pressure from 1to 100 atmospheres, and releasing the adsorbed ethylene and/or propyleneby lowering pressure and/or increasing temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 shows the adsorption breakthrough curve for ethylene andethane.

[0011]FIG. 2 shows the semi-continuous adsorption-desorption cycles forethylene-ethane mixture.

DETAILED DESCRIPTION OF THE INVENTION

[0012] The adsorbents of this invention are obtained by dispersion ofsilver compound and/or a promoter on the surface of a suitable supporthaving a high surface area by the action of a surface reaction betweensilver compound and the support which have been brought into contactwith each other. Many silver(I) compounds or silver(II) compounds ortheir mixtures can be used as silver compound. When silver (II)compounds are used as silver compound, silver(II) needs to be reduced tosilver(I) in a reducing atmosphere. Some of the representative examplesof the silver compound which can be suitably utilized in the practice ofthis invention include, for example, silver nitrate, silver halides suchas silver chloride, silver bromide and silver iodide, silvercarboxylates such as silver formate and silver acetate, and silveroxide. Preferred silver compounds are silver nitrate and silver acetate.As promoters rare earth metallic compounds such as lanthanum compoundsand cerium compounds or mixture thereof can be used. Some of therepresentative examples of promoter compounds are lanthanum(III)nitrate, lanthanum(III) chloride, cerium(III) chloride and cerium(III)nitrate.

[0013] As the support used to produce the adsorbents of this invention,a fairly large class of solid materials can be utilized provided thatthey have a sufficiently high surface area and have an affinity to thesilver compound. It is desirable in the preparation of the adsorbentsaccording to the present invention that the surface area of thosematerials used as a support is greater than 100 m²/g, preferably greaterthan 400 m²/g. Some representative examples of those materials that canbe used as the support for the adsorbent of this invention includealuminum oxide, natural or synthetic zeolites such as zeolite A, zeoliteY, and ZSM-5, microporous aluminum phosphates, clay minerals, and thelike.

[0014] In the process for the preparation of the adsorbent according tothe present invention, a mixture containing the silver compound, anoptional promoter, and a support is used. The above mixture can beobtained by adding to the support a solution or suspension of the silvercompound in a suitable solvent and optionally promoter compound,equilibrating for a period of 0.1 to 24 hrs preferably for 1 to 4 hrs,and thereafter removing the solvent from the resultant mixture byheating and (or) purging with air/inert gas. Representative examples ofthe solvent that can be suitably used include, for example, water,hydrochloric acid containing aqueous solution, primary or secondaryalcohols having 1 to 7 carbon atoms, acetone, ethyl acetate,hydrocarbons having 4 to 7 carbon atoms, propionitrile, andacetonitrile. The mixture can also be obtained by physically mixingsilver compound and optionally promoter compound in solid form to solidsupport.

[0015] In the above described mixture containing the silver compound andthe support, the amount of silver in the form of the compound ispreferably from 1 to 150%, more preferably from 10 to 80%, by weight ofthe support. Thereafter, the prepared mixture containing the silvercompound, optionally promoter compound, and the support is subjected toheating. The heating step can be performed at a temperature in the rangeof 30 to 500° C., preferably at 100 to 250° C. for a period of time fromabout 0.1 to about 48 hrs, preferably from about 1 to 10 hrs. Theheating step can be conducted in a suitable atmosphere such as nitrogenand helium.

[0016] The adsorbents of this invention described above can be used toseparate ethylene or propylene from mixed gas. The separation processcomprises passing a stream of the mixed gas through an adsorber bedcharged with the adsorbent(s) of the invention. The adsorbed ethyleneand/or propylene can be readily desorbed either by lowering the pressureor by increasing the temperature of the adsorber bed resulting in aregenerated adsorbent. The adsorbent so regenerated can be reused as anadsorbent for the separation of ethylene and/or propylene from the mixedgases. Raw material gases wherein ethylene and/or propylene present asimpurities can be purified by this separation process.

EXAMPLES

[0017] The invention is hereafter illustrated by the following examplesin detail. All of the given examples are merely for the purpose ofillustration and are not to be regarded as limiting the scope of theinvention or the manner in which it can be practiced.

[0018] The adsorption capacity and selectivity data involved in theseexamples were obtained by measuring adsorption isotherms in Cahn 1100microbalance system. In a typical adsorption isotherm measurement, aknown quantity of the adsorbent was loaded in the reactor tube andactivated under the flow of helium gas at 200° C. for several hours. Theadsorbent was then cooled to the desired adsorption temperature underhelium flow. The reactor tube was then evacuated to 1 04 mm Hg using atwo stage turbo molecular pump. Isotherm was then measured by admittingpulses of pure hydrocarbon gas into the reactor tube. After eachadsorption isotherm measurement, desorption experiment was also carriedout to check the reversibility of the adsorption isotherm.

Example 1

[0019] Silver nitrate solution prepared by dissolving 2.014 g of silvernitrate in 2.5 ml demineralized water was thoroughly mixed with 2.0 mmdiameter beads of 5.479 g of γ-Al₂O₃ (gama-alumina) and allowed toequilibrate for 2 hrs at room temperature. The said γ-Al₂O₃ had asurface area of 460 m²/g and was commercially available. The solutionwas just enough to wet all the solid. The wet adsorbent was dried atroom temperature by purging with helium gas. The resultant adsorbent wasdried at 110° C. for 6 hrs followed by calcination at 250° C. for 6 hrsunder helium flow. The adsorbent of 1 g adsorbed 0.76 mmol ethylene at25° C. and 760 mm Hg pressure of ethylene within 10 min. The adsorbedethylene was completely desorbed by evacuation at 100° C. The adsorbentwas able to adsorb the same amount of ethylene under the sameconditions. Under the same experimental conditions the adsorbent wasable to adsorb only 0.11 mmol of ethane. The adsorption selectivityratio of the adsorbent for ethylene to ethane was 6.9. Ethyleneadsorption selectivity over ethane on the alumina support was 1.2.

Example 2

[0020] Silver nitrate solution prepared by dissolving 2.0056 g of silvernitrate in 4.5 ml demineralized water was thoroughly mixed with 2.0 mmdiameter beads of 5.0054 g of γ-Al₂O₃ and allowed to equilibrate for 1hr at room temperature. The said γ-Al₂O₃ had a surface area of 460 m²/g.The excess solvent was dried at room temperature by purging with heliumgas. The resultant adsorbent was further dried at 110° C. for 6 hrsfollowed by calcination at 250° C. for 4 hrs under helium flow. Theadsorbent of 1 g adsorbed 1.00 mmol ethylene at 25° C. and 760 mm Hgpressure of ethylene within 10 min. The adsorbed ethylene was completelydesorbed by evacuation at 100° C. The adsorbent was able to adsorb thesame amount of ethylene under the same conditions. Under the sameexperimental conditions the adsorbent was able to adsorb only 0.16 mmolof ethane. The adsorption selectivity ratio of the adsorbent forethylene to ethane was 6.3. The same adsorbent after activating at 200°C. for 4 hrs adsorbed 1.22 mmol/g and 0.90 mmol/g of propylene at 760 mmHg pressure and 25° C. and 60° C. respectively. The adsorbed propylenewas completely desorbed under vacuum at 100° C. Under the sameexperimental conditions the adsorbent adsorbed only 0.43 mmol/g and 0.25mmol/g of propane at 25° C. and 60° C. respectively.

Example 3

[0021] Silver nitrate solution prepared by dissolving 2.2524 g of silvernitrate in 4.2 ml demineralized water was mixed with 2.0 mm diameterbeads of 5.0139 g of γ-Al₂O₃ and allowed to equilibrate for 1 hr at roomtemperature. The said γ-Al₂O₃ had a surface area of 460 m²/g. The excesssolvent was dried at room temperature by purging with helium gas. Theresultant adsorbent was further dried at 110° C. for 4 hrs followed bycalcination at 250° C. for 6 hrs under helium flow. The adsorbent of 1 gadsorbed 0.85 mmol of ethylene at 25° C. and 760 mm Hg pressure ofethylene within 10 min. The adsorbed ethylene was completely desorbed byevacuation at 100° C. The adsorbent was able to adsorb the same amountof ethylene under the same conditions. Under the same experimentalconditions the adsorbent was able to adsorb only 0.16 mmol of ethane.The adsorption selectivity ratio of the adsorbent for ethylene to ethanewas 5.3.

Example 4

[0022] Silver nitrate solution prepared by dissolving 6.2152 g of silvernitrate in 5.2 ml demineralized water was thoroughly mixed with 2.0 mmdiameter beads of 5.479 g of γ-Al₂O₃ and allowed to equilibrate for 2hrs at room temperature. The said γ-Al₂O₃ had a surface area of 360m²/g. The solution was just enough to wet all the solid. The wetadsorbent was dried at room temperature by purging with nitrogen for 30min. The resultant adsorbent was further dried at 110° C. for 2 hrsfollowed by calcination at 250° C. for 2 hrs under nitrogen atmosphere.The adsorbent of 1 g adsorbed 0.52 mmol ethylene at 25° C. and 760 mm Hgpressure of ethylene within 10 min. The adsorbed ethylene was completelydesorbed by evacuation at 100° C. The adsorbent was able to adsorb thesame amount of ethylene under the same conditions. Under the sameexperimental conditions, the adsorbent was able to adsorb only 0.10 mmolof ethane. The adsorption selectivity ratio of the adsorbent forethylene to ethane was 5.2.

Example 5

[0023] Silver nitrate solution prepared by dissolving 3.148 g of silvernitrate and 0.6662 g of lanthanum nitrate hexahydrate in 2.75 mldemineralized water was thoroughly mixed with 2.0 mm diameter beads of5.0161 g of γ-Al₂O₃ and allowed to equilibrate for 2 hrs at roomtemperature. The said γ-Al₂O₃ had a surface area of 360 m²/g. The wetadsorbent was dried at room temperature by purging with helium gas for30 min. The resultant adsorbent was further dried at 11 0C for 4 hrsfollowed by calcination at 350° C. for 6 hrs under helium flow. Theadsorbent of 1 g adsorbed 0.57 mmol ethylene at 25° C. and 760 mm Hgpressure of ethylene within 10 min.

Example 6

[0024] Lanthanum nitrate hexahydrate solution prepared by dissolving3.3343 g of lanthanum nitrate hexahydrate in 18 ml demineralized waterwas thoroughly mixed with 2.0 mm diameter beads of 30.0092 g of γ-Al₂O₃and allowed to equilibrate for 1 hr at room temperature. The saidγ-Al₂O₃ had a surface area of 460 m²/g. The wet adsorbent was dried atroom temperature by purging with helium for 1 hr. The resultantadsorbent was further dried at 110° C. for 4 hrs followed by calcinationat 250° C. for 6 hrs under helium atmosphere.

Example 7

[0025] Silver nitrate solution prepared by dissolving 2.2540 g of silvernitrate in 4.2 ml demineralized water was thoroughly mixed with 5.0178 gof the adsorbent obtained in Example 6 and equilibrated for 1 hr. Thewet adsorbent was dried at room temperature with helium purge for 30min. The resultant adsorbent was further dried at 11 0C for 4 hrsfollowed by calcination at 250° C. for 6 hrs under helium atmosphere.The adsorbent of 1 g adsorbed 0.92 mmol ethylene at 25° C. and 760 mm Hgpressure of ethylene within 10 min. The adsorbed ethylene was completelydesorbed by evacuation at 100° C. The adsorbent was able to adsorb thesame amount of ethylene under the same conditions. The adsorptionselectivity ratio of the adsorbent for ethylene to ethane was 6.4.

Example 8

[0026] Silver nitrate solution prepared by dissolving 1.4104 g of silvernitrate in 3.04 ml demineralized water was thoroughly mixed with 3.556 gof the adsorbent obtained in Example 6 and equilibrated for 1 hr. Thewet adsorbent was dried at room temperature with helium purge for 30min. The resultant adsorbent was further dried at 110° C. for 4 hrsfollowed by calcination at 250° C. for 6 hrs under helium atmosphere.The adsorbent of 1 g adsorbed 0.97 mmol ethylene at 25° C. and 760 mm Hgpressure of ethylene within 10 min. The adsorbed ethylene was completelydesorbed by evacuation at 110° C. The adsorbent was able to adsorb thesame amount of ethylene under the same conditions. The adsorptionselectivity ratio of the adsorbent for ethylene to ethane was 3.2.

Example 9

[0027] 1.0 g of 2.0 mm diameter beads of γ-Al₂O₃ was finely ground (100μm) in a mortar and pestle. This powder was mixed with 0.45 g ofsilver nitrate and heated at 250° C. for 6 hrs in helium atmosphere. Theproduct was adsorbent in powder form which adsorbed 0.86 mmol ethyleneper gram of the adsorbent at 25° C. and 760 mm Hg pressure of ethylenewithin 10 min. The adsorbed ethylene was completely desorbed byevacuation at 100° C.

Example 10

[0028] Silver nitrate solution prepared by dissolving 2.0045 g of silvernitrate in 5.1 ml demineralized water was thoroughly mixed with 5˜10mesh diameter beads of 5.1054 g of silica gel and allowed to equilibratefor 1 hr at room temperature. The said silica gel had a surface area of425 m²/g. The excess solvent was dried at room temperature by purgingwith helium gas. The resultant adsorbent was further dried at 110° C.for 6 hrs followed by calcination at 250° C. for 4 hrs under heliumflow. The adsorbent of 1 g adsorbed 0.50 mmol ethylene at 25° C. and 760mm Hg pressure of ethylene within 10 min. The adsorbed ethylene wascompletely desorbed by evacuation at 100° C.

Example 11

[0029] 1.0 g of zeolite X was mixed with 0.45 g of silver nitrate andthen heated at 250° C. for 24 hrs in helium atmosphere. The productadsorbent which adsorbed 2.5 mmol of ethylene per gram of the adsorbentat 25° C. and 760 mm Hg of ethylene. The adsorbent had ethyleneselectivity ratio over ethane of 2.1.

Example 12

[0030] 1.0 g of zeolite Y with Si/Al=20 was mixed with 0.5 g of silvernitrate and then heated at 250° C. for 24 hrs in helium atmosphere. Theproduct adsorbent which adsorbed 1.8 mmol of ethylene per gram of theadsorbent at 25° C. and 760 mm Hg of ethylene. The adsorbent hadethylene selectivity ratio over ethane of 2.3.

Example 13

[0031] Silver acetate solution prepared by dissolving 2.2500 g of silveracetate in 5.0 ml demineralized water was mixed with 2.0 mm. diameterbeads of 5.0036 g of γ-Al₂O₃ and allowed to equilibrate for 1 hr at roomtemperature. The said γ-Al₂O₃ had a surface area of 460 m²/g. The excesssolvent was dried at room temperature by purging with helium gas. Theresultant adsorbent was further dried at 110° C. for 4 hrs followed bycalcination at 250° C. for 6 hrs under helium flow. The adsorbent of 1 gadsorbed 0.88 mmol of ethylene at 25° C. and 760 mm Hg pressure ofethylene within 10 min. The adsorbed ethylene was completely desorbed byevacuation at 100° C. The adsorbent was able to adsorb the same amountof ethylene under the same conditions.

Example 14

[0032] 100 g of the adsorbent was prepared in the same manner asdescribed in Example 3. 68.4 g of this adsorbent on an ambient basis waspacked in a stainless steel column of 250 mm height and 20 mm diameter(78.5 ml internal volume). The adsorbent was activated at 200° C. for 3hrs under helium flow, and then the column was filled with helium up to770 mm Hg with temperature reduction to 24° C. Feed mixture consistingof 70.5% of ethylene and 29.5% of ethane by volume was allowed to passthrough the adsorbent bed with feed flow rate of 150 sccm at 800 mm Hg.The adsorption breakthrough curve for ethylene and ethane is shown inFIG. 1. In the first 540 sec, the concentration of ethylene in theoff-gas was lower than 0.01% by volume. The dynamic adsorption capacityof ethylene on the above adsorbent as obtained by breakthrough curve was0.76 mmol/g (at 560 mm Hg). The adsorbed ethylene could be completelydesorbed by evacuation to 30 mm Hg at 100° C.

Example 15

[0033] Semi-continuous adsorption-desorption cycles for saidethylene-ethane mixture were performed at 60° C. on the adsorptioncolumn described in Example 14. It was carried out in a four stepsemi-continuous cycles consisting of (a) ethane re-pressurization, (b)adsorption with feed, (c) ethylene rinse, and (d) vacuum desorption. Thetime gaps between each step were 1˜5 min. Step time, flow rate and bedpressure during each step are given below: Step Time/sec Flow rate/sccmPressure/mmHg Ethane re-pressurization  35 250 up to 772 Adsorption 330150 760 to 780 Ethylene rinse  90 100 770 Vacuum desorption 480 —  30

[0034] The results are shown in FIG. 2. The data by this cyclicadsorption-desorption experiments was reproducible, which ensured theexistence of steady state conditions. The purity of the effluent ethanegas was 97.5˜99.0%. The breakthrough time was 220 sec compared to 540sec of a fresh adsorbent. Purity of ethylene product obtained was atleast 95%.

REFERENCES CITED

[0035] 1. Keller, G. E; Marcinkowsky, A. E.; Verma, S. K.; Williamson,K. D., Olefin Recovery and Purification via Silver Complexation., InSeparation and Purification Technology, Li, N. N., Calo, J. M., Eds.,Marcel Dekker, New York, 1992.

[0036] 2. Eldridge, R. B., Olefin/Paraffin Separation Technology: AReview., Ind. Eng. Chem. Res., 32, 2208,1993.

[0037] 3. Gilliland, E. R.; Bliss, H. L.; Kip, C. E. Reaction of Olefinswith Solid Cuprous Halide, J. Am. Chem. Soc., 63, 2088,1941.

[0038] 4. Gilliland, E. R. Concentration of Olefins. U.S. Pat. No.2,369,559, 1945.

[0039] 5. Long, R. B. Separation of Unsaturates by Complexing with SolidCopper Salts. In Recent Development in Separation Science; Li, N. N.Ed., CRC Press, Cleveland, 1972.

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[0041] 7. Rosback, D. H., Adsorbing Olefins with a Copper-Exchanged TypeY Zeolite. U.S. Pat. No. 3,720,604, 1973.

[0042] 8. Yang, R. T.; Kikkinides, E. S. New Sorbents forOlefin/Paraffin Separations by Adsorption via π-Complexation. AlChE J.,41, 509, 1995.

[0043] 9. Hirai, H.; Kurima, K.; Wada, K.; Komiyama, M., SelectiveEthylene Adsorbents Composed of Copper(I) Chloride and PolystyreneResins Having Amino Groups. Chem. Lett., 1513,1985.

[0044] 10. Hirai, H.; Hara, S.; Komiyama, M. Polystyrene-SupportedAluminum Silver Chloride as Selective Ethylene Adsorbent. Angew.Makromol. Chem., 130, 207,1985.

[0045] 11. Hirai, H., Polymer Complex for the Separation of CarbonMonoxide and Ethylene. In Polymers for Gas Separation; Toshima, N. Ed:,VCH Publishers Inc., New York, Chapter 7,1992.

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[0047] 13. Wu, Z.; Han, S. S.; Cho, S. H.; Kim, J. N.; Chue, K. T.;Yang, R. T., Modification of Resin-Type Adsorbents for Ethane/EthyleneSeparation, Ind Eng. Chem. Res., 36, 2749,1997.

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[0050] The above references are hereby incorporated by reference.

We claim:
 1. An adsorbent for use in selective adsorption of unsaturatedhydrocarbons or mixtures thereof from a mixed gas, said adsorbentcomprising: (a) a suitable support having a sufficiently high surfacearea, and (b) a silver compound.
 2. The adsorbent of claim 1 furthercomprising a promoter compound on the support.
 3. The adsorbent of claim1 wherein said adsorbent is prepared by dissolving said silver compoundin a suitable solvent, drying of excess solvent to produce a solidmaterial, and heat treatment of the solid material.
 4. The adsorbent ofclaim 1 wherein said support is selected from the group consisting of analumina, a zeolite and a silica gel in powder or pellet/bead form. 5.The adsorbent of claim 1 wherein said silver compound is selected fromthe group consisting of silver nitrate, silver carboxylate, silverhalide, silver oxide, and a mixture thereof.
 6. The adsorbent of claim 2wherein said promoter compound is selected from the group consisting oflanthanum nitrate, lanthanum chloride, cerium chloride, cerium nitrate,and a mixture thereof.
 7. The adsorbent of claim 1 wherein said silvercompound is present at from about 2% to 100% by weight of said support.8. The adsorbent of claim 2 wherein said promoter compound is present atfrom about 2% to 20% by weight of said support.
 9. The adsorbent ofclaim 3 wherein the solvent is selected from the group consisting ofwater, alcohols, hydrocarbons, and aqueous hydrochloric acid.
 10. Theadsorbent of claim 1 wherein said heat treatment is carried out at atemperature in the range of 30 to 350° C.
 11. The adsorbent of claim 1which adsorbs at least 0.5 mmol of ethylene or propylene per gram ofadsorbent at ambient temperature and 760 mm Hg and adsorptionselectivity of ethylene over ethane or propylene over propane is atleast
 5. 12. A process for the separation of olefin molecules ormixtures thereof from a mixed gas containing olefin molecules or amixture thereof, wherein the mixed gas comprises a component selectedfrom the group consisting of H₂, He, CH₄, C₂H₆, C₃H₈, and mixturesthereof, wherein said process comprises: a) passing the mixed gasthrough the adsorbent of claim 1 at a temperature in the range of from0° C. to 100° C. and a pressure in the range from 1 to 100 atmospheres,and b) releasing the adsorbed ethylene and/or propylene.
 13. The processof claim 12 wherein the releasing is accomplished by lowering thepressure and/or heating the adsorbent.
 14. A method for the manufactureof an adsorbent for use in selective adsorption of unsaturatedhydrocarbons or mixtures thereof from a mixed gas, comprising a)providing a composition comprising a silver compound in a suitablesolvent, b) providing a support material having a sufficiently highsurface area, c) impregnating said composition on said support material,d) drying of excess solvent to produce a solid material, and e) heattreatment of the solid material.
 15. The method of claim 14, whereinsaid support material is selected from the group consisting of analumina, a zeolite and a silica gel in powder or pellet/bead form. 16.The method of claim 14 wherein said silver compound is selected from thegroup consisting of silver nitrate, silver carboxylate, silver halide,silver oxide, and a mixture thereof.
 17. The method of claim 14 whereinthe solvent is selected from the group consisting of water, alcohols,hydrocarbons, and aqueous hydrochloric acid.
 18. The method of claim 14,wherein the composition of a) further comprises a promoter compound. 19.The method of claim 18 wherein said promoter compound is selected fromthe group consisting of lanthanum nitrate, lanthanum chloride, ceriumchloride, cerium nitrate, and a mixture thereof.